Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: De-embedding lossy transmission line Posted: Wed Jul 25, 2007 4:40 pm
Joined: Wed Jul 25, 2007 4:23 pm
Hi all experts ,
I'm doing the
I have a system which consists of a pair of SMA cables, backplane with microstrip
differential pair and another pair of cables which S-parameters I'm trying to find.
Unfortunately, I can't
just measure S-parameters of the second pair of cables by using a VNA. But I have S-parameters of the whole
system: [SMA cables - backplane - cables], and S-parameters of [SMA cables] and [backplane] separately. The
backplane is relatively ‘lossy’ at high frequencies (>10GHz).
I'm converting S-parameters to T-parameters,
then taking T[backplane]^-1*T[SMA-cables]^-1*T[whole system]. Then, I’m converting back to S expecting to get
"second" cables S matrix. Beyond some frequency (~12GHz), I'm getting very high gain and obviously wrong behavior.
I used this technique in the past to de-embed NOT very ‘lossy’ components...
What could be wrong?
lot in advance,
Post subject: Posted: Thu Jul 26, 2007 3:39 am
Joined: Fri Feb 17, 2006 12:07 pm
Location: London UK
time I encountered something similar, where a VNA plot turned to rat doo-dooz above a certain frequency, it turned
out to be an unexpected resonance. This produced a rapid variation in S parameters around the resonant frequency,
and at harmonics of it.
Is there any chance your set-up could exhibit a resonance?